Is it because of some ferrite stabilizer or something?A detailed explanation to this is most welcome.
Depends what you mean by "manganese steel". If you mean a low alloy like AISI 1100 types , you are above the curie temperature or you are measuring wrong . If you mean a Hadfield type ( 11 to 14 % Mn) it cooled quickly enough to be mostly retained austenite . It certainly has nothing to do with ferrite stabilizing as that would be magnetic. Because railroad applications are the main use of Hadfield types , I suspect that is what you have. I suggest getting a book that covers Hadfield type alloys for details. These steels are relatively uncommon.